Enhanced security checks mean any electronic devices that will not switch on will have to be left behind by passengers travelling to the US.

US homeland security confirmed that these checks would be implemented immediately at some airports abroad as it believes that there is a very real threat of terrorist attacks with the potential for phones to be turned into explosive devices that can avoid detection.

The US Transportation Security Administration warned: “Powerless devices will not be permitted onboard the aircraft. The traveller may also undergo additional screening.”

Conservative MP Sir Malcolm Rifkind warned against complacency on the issue because there are more threats than have been made public. Writing in The Sunday Telegraph, Sir Malcolm said: “It is simply foolish to believe that the threat is either minimal or now behind us.

“We have, indeed, been fortunate but, sadly, this has not been because the terrorists have, since 2005, given up trying to do us harm.”